A peptide-tethered lipid bilayer on mercury as a biomimetic system

A novel spacer consisting of a hexapeptide molecule with a high tendency to form a 3(10)-helical structure, which terminates with a sulfydryl group fo r anchoring to a metal, was tailored for use as a tethered hydrophilic spac er to be interposed between a metal support and a lipid bilayer. The thiol peptide has two triethylenoxy side chains that impart it a satisfactory hyd rophilicity and are intended to keep the anchored thiol peptide chains suff iciently apart so as to accommodate water molecules and inorganic ions and to create a suitable environment for the incorporation of integral proteins . This thiol peptide was anchored to a hanging mercury drop electrode. The formation of a phospholipid bilayer on top of the self-assembled thiol pept ide was carried out by a novel procedure which exploits the spontaneous ten dency of a lipid film to form a bilayer when interposed between two hydroph ilic phases. The resulting mercury-supported thiol peptide/lipid bilayer sy stem was characterized by ac voltammetry with phase resolution, chronocoulo metry, and impedance spectroscopy. The suitability of this tethered film as a biomembrane model was tested by incorporating ubiquinone-10 and valinomy cin.